DESCRIPTION: (Applicant's Abstract) The long term objective of this revised research project is to examine differences in tobacco craving and dependence in recovering polysubstance users versus smokers without a history of other dependence/abuse as a initial step towards developing effective treatments for smoking cessation in these populations whose health is synergistically compromised by multiple risk factors. Specific aims include: 1) assessment of tobacco craving among 2 subtypes of smokers; 2) assessment of tobacco dependence among 2 subtypes of smokers; 3) determination of differences in nicotine preference among groups; and finally, 4) exploration of the relationship between craving, history of drug dependence and nicotine self administration. The large study originally proposed has been substantially modified; two smaller studies will now be conducted to address the reviewers' concerns. Laboratory based assessments will be conducted in a state-of-the-art human behavioral pharmacology paradigm. Each assessment has demonstrated psychometric soundness. In study one, subjects complete tobacco craving and dependence measures under tobacco deprived and non-deprived conditions. Self-reported compliance is validated by experimenter observations and biochemical measurement. In study two, subjects undergo a nicotine selfadministration trial in a protocol that was previously validated in deprived current smokers with no intention to quit (Hughes, Strickler, et al, 1989). These data will be among the first to examine differences in tobacco craving and dependence among subtypes of smokers in a laboratory setting.